Endothelial cells covering the inner surface of blood vessels are continuously exposed to mechanical forces associated with blood flow, which can be resolved into two components; shear stress, a tangential frictional force which acts at the endothelial cell surface, and cyclic strain, acting perpendicular to the vascular wall. Blood flow is an important determinant of vascular remodeling in endothelial intact and denuded vessels with reduce flow predisposing arteries to intimal thickening and atherosclerosis. Fluid shear stress and cyclic strain modulate endothelial function by stimulating the secretion of several factors from endothelial cells including nitric oxide (NO), prostacyclin (PGI2), transforming growth factor (TGFbeta), basic fibroblast growth factor (bGFG), endothelin, and platelet-derived growth (PDGF) that can modulate the underlying vascular smooth muscle cell growth and function. The central hypothesis of this proposal is that sustained increased ion flow modulate the growth of the underlying smooth muscle by differentially decreasing the release of mitogenic and increasing the release of anti- mitogenic substances from endothelial cells. This First Award application proposes to define the acute and chronic effects of flow on endothelial cell function and the subsequent consequences on the growth of the underlying smooth muscle. Utilizing our novel perfused transcapillary co-culture system, whereby endothelial and vascular smooth muscle cells can be simultaneously chronically exposed to physiological shear stress and cyclic strain (pulsatile flow), we will define the acute and chronic effects of flow on: (i) endothelial release of anti-mitogenic substances (NO, PGI2, and TGFbeta) and mitogenic substances (PDGF, bFGF and endothelin) in co- cultured cells (ii) endothelial control of mitogen-activated protein kinase signaling (MAPK's and p34/cdc2) and growth in the underlying vascular smooth muscle: the role of NO, PGI2 and TGFbeta. (iii) mitogen activated protein kinase signaling (MAPK's and p34/cdc2_ and growth in vascular smooth muscle cells in the absence of endothelial cells; the role of TGFbeta, PDGF, bFGF and MMP,s. It is critical to define the role of mechanical force on endothelial control of smooth muscle cell growth because the vascular endothelium is though to play a pivotal role in regulating smooth muscle cell growth in vivo and because flow has significant effect on several aspects of endothelial function. These experiments should provide valuable information central to our understanding of the important role hemodynamic forces play in vascular biology,a nd thus further our knowledge of its role in the etiology of cardiovascular disease.